title: Linkage and sequence homology of two human immunoglobulin gamma heavy chain constant region genes.
abstract: We report the nucleotide sequence of a gene encoding a human immunoglobulin C gamma 2 region. Comparison with the previously determined C gamma 4 sequence reveals that these two genes share extensive (approximately 95%) homology in the three CH domain exons and adjacent noncoding regions. In contrast, hinge exons have diverged to a much greater degree, implying that natural selection has favored the generation of diversity in these coding regions. We have used the noncoding nucleotide differences to estimate that approximately 6-7 million years have elapsed since the occurrence of the gene duplication or correction event which generated the two identical ancestral genes. In addition we show that the two C gamma genes are arranged in human chromosomal DNA in the configuration 5'-C gamma 2-17 kilobase pairs -C gamma 4-3'.
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D005075:Biological Evolution; D002874:Chromosome Mapping; D005796:Genes; D008040:Genetic Linkage; D006801:Humans; D007127:Immunoglobulin Constant Regions / Q000235:genetics*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007142:Immunoglobulin gamma-Chains / Q000235:genetics*; D007136:Immunoglobulins / Q000235:genetics*
chemical_list: D007127:Immunoglobulin Constant Regions; D007143:Immunoglobulin Heavy Chains; D007142:Immunoglobulin gamma-Chains; D007136:Immunoglobulins